DE102021215068A1 - Compensating device and method for compensating for a focus shift of an optical system and method for manufacturing a compensating device - Google Patents

Abstract

The approach presented here relates to a compensation device (100) for compensating for a focus shift in an optical system. The compensation device (100) has the optical system (300) and an optical compensation element (110). The optical system (300) has an optical element (115), in particular a lens, and an image sensor (120), which are arranged in a common beam path (125) that is focused on a focal point (127). The optical compensation element (110) is arranged in the beam path (125) and designed to change an optical effect in response to at least one environmental parameter in order to shift the focal point (127) in order to compensate for the shift in focus.

Description

State of the art

The approach is based on a device or a method according to the species of the independent claims. The subject of the present approach is also a computer program.

The DE 10 2008 027 721 A1 discloses an approach to producing a mechanical holding structure for a lens with a material that expands as a function of temperature and thereby to achieve compensation for a temperature-dependent change in the refractive index of a lens of the optical system.

Disclosure of Invention

Against this background, with the approach presented here, a compensation device for compensating for a focus shift of an optical system, a method for compensating for a focus shift of an optical system, a method for producing a compensation device, also a device that uses one of the methods, and finally a corresponding computer program presented according to the main claims. Advantageous developments and improvements of the device specified in the independent claim are possible as a result of the measures listed in the dependent claims.

The advantages that can be achieved with the approach presented are that using a single additional compensation element in an optical system, a focus shift in the optical system caused by temperature or moisture, for example, can be compensated for quickly and easily in order to close the focal point near the image sensor of the optical system hold.

A compensation device for compensating for a focus shift of an optical system is presented. The compensation device has the optical system and an optical compensation element. The optical system has an optical element, in particular a lens, a compensation element and/or an image sensor, which are arranged in a common beam path that is focused on a focal point. The optical element can be a lens or another element that also has one or more mirrors, for example. The optical compensation element is arranged in the beam path and is designed to change an optical effect in response to at least one environmental parameter, in order to shift the focal point in order to compensate for the shift in focus of the optical system.

The optical system can be a camera that can be used in a vehicle, for example, as a so-called “automotive camera”. The focus shift/defocusing of the optical system can be temperature-related or moisture-induced, for example, and can result in the focus point being located in an area too far away from the camera's image sensor. This can happen, for example, when components such as the optical element or the lens or a lens mount, a lens spacer or a lens element and/or the image sensor or an image sensor mount of the optical system physically expand or contract due to temperature or humidity and the focus of the optical system thus move or change. It is also conceivable that the elements mentioned here can not only expand or contract, but can also change the refractive index and radius. Overall, this leads to a shift in focus. The compensation element can now advantageously be used to track the focus point in accordance with or similar to the focus shift, so that the focus point is arranged in the focal range of the optical system and a sharp image is produced.

The optical compensation element can be arranged directly, for example immediately, in the focused beam path, for example between the optical element or lens and the image sensor. The optical compensation element can be designed to change the optical effect in the form of a change in shape and/or a change in the refractive index of the optical compensation element in response to the environmental parameter in order to compensate for the focus shift of the optical system. For example, the compensation can take place in that the optical compensation element effects a tracking of the focus point corresponding to or similar to the focus shift. Thanks to the compensation element, defocusing of the camera can thus be improved, for example at least partially compensated for. Due to the shift in focus, the sensor is no longer in the depth of field of the camera, so that compensation means that the sensor is again in the depth of field of the camera. Thanks to the compensation element, the image sensor remains in the depth of field, which can cover a range from 1 to 1000 μm, for example, even if there is a shift.

According to one embodiment, a displacement parameter Δz ₁ of the optical compensation element representing a displacement of the focus point can correspond within a tolerance range to a further displacement parameter Δz ₂ of a system comprising the optical element, a holding element of the optical element and/or the image sensor, the displacement parameter depending on a refractive index and an expansion coefficient. The compensation element can be deformable thermally, moisture-induced and/or stress-induced, for example by applying an electrical voltage, and/or be designed to change the refractive index or a shift of the focus point thermally, moisture-induced and/or stress-induced. Analogously, the system comprising the optical element, the holding element of the optical element and/or the image sensor can also be deformable and/or designed to reduce the refractive index or a shift due to thermal, moisture-induced and/or stress-induced stress, for example by applying an electrical voltage of the focal point due to thermal, moisture-induced and/or stress-induced changes. The tolerance range can include, for example, a deviation of the displacement parameter of the compensation element from the displacement parameter of the system, that of the lens or the retaining element of the lens and/or the image sensor or the retaining element of the image sensor, of up to 35%.

According to one embodiment, the optical compensation element can have a material that is designed to expand in a defined temperature range, humidity range and/or electrical voltage range with a predetermined coefficient of expansion. In addition, an expansion can also occur together with a change in the refractive index, which also partially compensate each other and therefore both effects should be taken into account. Also, the refractive index change can be the driving force. Correspondingly, the material of the optical compensation element can be designed to contract in a further lower temperature range, humidity range and/or electrical voltage range. It can thus be predetermined in which temperature range, humidity range and/or electrical voltage range a desired expansion of the compensation element takes place. For example, a greater expansion can take place within a higher temperature range, a higher humidity range and/or greater electrical voltage range than within a lower temperature range, a lower humidity range and/or lower electrical voltage range.

The optical compensation element can have at least one plane-parallel plate and/or be designed as a plane-parallel plate. The plane-parallel plate can have a thickness of between 0.1 millimeter and 5 millimeters, for example a thickness of 1 millimeter. Plane-parallel plates are insensitive to decentering and changes in position in the z-direction.

The optical compensation element can additionally or alternatively have at least one lens and/or be designed as a lens. Lens elements can further improve the optical performance of the system.

In accordance with one embodiment, the compensation element can have an optically transparent material and/or be embodied as an optically transparent material. In this way, a simple and quick compensation of the focus shift can be implemented.

The compensation element can be formed at least partially from plastic. The compensation element can also be formed entirely from plastic. This enables a variant for the compensation element that is light and inexpensive to produce. The compensation element can be formed in one piece and/or from one material, for example.

According to one embodiment, the compensation element can be arranged in direct contact with the image sensor. For example, a so-called “lens-on-chip” can be implemented as a component. For example, the compensation element can be implemented as a replacement for a sensor cover glass or as an add-on to or as a replacement for an IR filter of the lens. It is to be understood as direct that, with the exception of an optional fastening material, no further component is contacted between the compensation element and the image sensor or lens.

A method for compensating for a focus shift of an optical system has a step of providing and a step of changing. In the providing step, an optical system with a lens and an image sensor, which are arranged in a common beam path that is focused on a focus point, and an optical compensation element arranged in the beam path are provided. In the changing step, an optical effect of the compensation element is changed in response to at least one environmental parameter in order to shift the focus point in order to compensate for the focus shift of the optical system. In the step of Changing an electrical voltage can be applied in response to the at least one environmental parameter in order to change the optical effect of the compensation element in order to shift the focus point in order to compensate for the focus shift of the optical system.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

A method for producing a compensation device for compensating for a focus shift of an optical system has a step of providing and a step of arranging. In the providing step, the optical system is provided with a lens and an image sensor, which are arranged in a common beam path that is focused on a focal point. In the arranging step, an optical compensation element is arranged in the beam path, the optical compensation element being designed to change an optical effect in response to at least one environmental parameter, in order to shift the focus point in order to compensate for the focus shift of the optical system.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a device that is designed to carry out, control or implement the steps of one of the methods presented above in corresponding devices. The task on which the approach is based can also be solved quickly and efficiently by this embodiment variant of the approach in the form of a device.

For this purpose, the device can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading in sensor signals from the sensor or for outputting data or control signals to the Have actuator and / or at least one communication interface for reading or outputting data that are embedded in a communication protocol. The arithmetic unit can be, for example, a signal processor, a microcontroller or the like, with the memory unit being able to be a flash memory, an EEPROM or a magnetic memory unit. The communication interface can be designed to read in or output data wirelessly and/or by wire, wherein a communication interface that can read in or output wire-bound data can, for example, read this data electrically or optically from a corresponding data transmission line or can output it to a corresponding data transmission line.

In the present case, a device can be understood to mean an electrical device that processes sensor signals and, depending thereon, outputs control and/or data signals. The device can have an interface that can be configured as hardware and/or software. In the case of a hardware design, the interfaces can be part of a so-called system ASIC, for example, which contains various functions of the device. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In the case of a software design, the interfaces can be software modules which are present, for example, on a microcontroller alongside other software modules.

A computer program product or computer program with program code, which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and/or controlling the steps of the method according to one of the embodiments described above, is also advantageous used, especially when the program product or program is run on a computer or device.

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer Kompensationsvorrichtung zum Kompensieren einer Fokusverschiebung eines optischen Systems;
• 2 eine schematische Darstellung einer thermisch bedingten Fokusverschiebung in einem optischen System;
• 3 eine schematische Gegenüberstellung einer Kompensationsvorrichtung gemäß einem Ausführungsbeispiel gegenüber einem optischen System ohne optischem Kompensationselement;
• 4 eine schematische Darstellung einer Fokusverschiebung durch ein optisches Kompensationselement, welches Brechzahl und Dicke abhängig von der Temperatur gemäß einem Ausführungsbeispiel ändert;
• 5 ein Ablaufdiagramm eines Verfahrens gemäß einem Ausführungsbeispiel zum Kompensieren einer Fokusverschiebung eines optischen Systems;
• 6 ein Ablaufdiagramm eines Verfahrens gemäß einem Ausführungsbeispiel zum Herstellen einer Kompensationsvorrichtung zum Kompensieren einer Fokusverschiebung eines optischen Systems.
• 7 ein Blockschaltbild einer Vorrichtung gemäß einem Ausführungsbeispiel zum Kompensieren einer Fokusverschiebung eines optischen Systems; und
• 8 ein Blockschaltbild einer Vorrichtung gemäß einem Ausführungsbeispiel zum Herstellen einer Kompensationsvorrichtung zum Kompensieren einer Fokusverschiebung eines optischen Systems.

Exemplary embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. Show it:

• 1 a schematic representation of an embodiment of a compensation device for compensating for a focus shift of an optical system;
• 2 a schematic representation of a thermally induced focus shift in an optical system;
• 3 a schematic comparison of a compensation device according to an embodiment compared to an optical system without an optical compensation element;
• 4 a schematic representation of a focus shift by an optical com compensation element, which changes refractive index and thickness depending on the temperature according to an embodiment;
• 5 a flowchart of a method according to an embodiment for compensating for a focus shift of an optical system;
• 6 a flowchart of a method according to an embodiment for producing a compensation device for compensating for a focus shift of an optical system.
• 7 a block diagram of a device according to an embodiment for compensating for a focus shift of an optical system; and
• 8th a block diagram of a device according to an embodiment for producing a compensation device for compensating for a focus shift of an optical system.

In the following description of favorable exemplary embodiments of the present approach, the same or similar reference symbols are used for the elements which are shown in the various figures and have a similar effect, with a repeated description of these elements being dispensed with.

1 shows a schematic representation of an embodiment of a compensation device 100 for compensating for a focus shift of an optical system.

The compensation device 100 has the optical system and an optical compensation element 110 . The optical system has an optical element 115 (such as a lens or a mirror or mirror system) and an image sensor 120, which are arranged in a common beam path 125, which is focused on a focal point 127. The optical compensation element 110 is arranged in the beam path 125 and is designed to change an optical effect in response to at least one environmental parameter in order to shift the focus point 127 in order to compensate for the focus shift of the optical system. The optical element 115 and the image sensor 120 (and optionally also the optical compensation element 110) are attached to a common holding element 128.

According to this exemplary embodiment, the optical system is a camera that can be used, for example, in a vehicle 130 . The focus of the optical system can be shifted, for example, due to temperature or moisture and result in the focal point 127 and the depth of field of the optical element or lens being outside the position of the image sensor 120 of the camera. This can happen, for example, if components such as the lens or optical element 115, the image sensor 120 of the optical system and/or a holding element 128 of the lens or optical element 115 and/or a holding element 128 of the image sensor 120 physically expand due to temperature or moisture , or corresponding radii, refractive index or lens positions change and thus shift the focus. A first beam path end section A between the compensation element 110 and the image sensor 120 shows an end section of the beam path 125 with an unchanged focus point, ie a focus point which was not shifted by means of the compensation element 110 . A second beam path end section B between compensation element 110 and image sensor 120 shows an end section of beam path 125 with focal point 127 shifted by means of compensation element 110.

According to this exemplary embodiment, the optical compensation element 110 is arranged directly, for example immediately, in the beam path 125, for example between the lens or optical element 115 and the image sensor 120. The optical compensation element 110 is designed according to this exemplary embodiment, in response to the environmental parameter, to To change effect in the form of a change in shape and / or a change in refractive index of the optical compensation element 110 to move the focus point 127 to cause the focus shift of the optical system. According to this exemplary embodiment, the compensation takes place in that the optical compensation element 110 effects a tracking of the focus point 127 in accordance with the focus shift/defocusing. Thanks to the compensation element 110, the image sensor 120 also remains in the depth of field, which in this case covers a range from 10 to 1000 μm, for example, see also 3 .

According to this exemplary embodiment, compensation element 110 has a material that includes a displacement parameter Δz ₁ of optical compensation element 110, which represents a displacement of focal point 127, within a tolerance range, a further displacement parameter Δz ₂ of an optical element, a holding element of the optical element, and/or the image sensor corresponds to the system, the displacement parameter depending on a refractive index and an extension According to this exemplary embodiment, the compensation element 110 is thermally induced, moisture-induced and/or stress-induced, for example by applying an electrical voltage, deformable and/or is designed to change the refractive index thermally, moisture-induced and/or stress-induced. The tolerance range can include, for example, a deviation of the displacement parameter Δz ₁ of the compensation element 110 from the expansion coefficient of the displacement parameter Δz ₂ of the lens or optical element 115, image sensor 120 and/or the holding element 128 of up to 35%.

According to this exemplary embodiment, the compensation element 110 has a refractive index of 1.51 with thermal expansion coefficients of at least 50 ppm/K. With such a coefficient of thermal expansion, heating from 20° to 105° C. produces a 4.05 μm shift with a thickness of 1 mm and thus refocusing. This can significantly improve the sharpness of the entire camera system.

According to this exemplary embodiment, the compensation element 110 has a material that is designed to expand in a defined temperature range, humidity range and/or electrical voltage range with a predetermined coefficient of expansion. Correspondingly, the material of the optical compensation element 110 according to one exemplary embodiment is designed to contract in a further, lower temperature range, humidity range and/or electrical voltage range. According to this exemplary embodiment, there is a greater or reduced expansion within a higher temperature range, a higher humidity range and/or greater electrical voltage range than within a lower temperature range, a lower humidity range and/or lower electrical voltage range. Furthermore, an index of refraction and/or an extension can also change together and also act together, although possibly not in the same direction.

According to this exemplary embodiment, the compensation element 110 has at least one plane-parallel plate and/or is designed as a plane-parallel plate. The plane-parallel plate can have a thickness between 0.1 millimeter and 10 millimeters, for example 1 millimeter. According to an alternative exemplary embodiment, the compensation element 110 additionally or alternatively has at least one lens with at least one curved or arched surface and/or is designed as a lens. In this context, a lens can be understood as an element that does not necessarily have a sphere; a free form is certainly also possible.

According to this exemplary embodiment, the compensation element 110 has an optically transparent material and/or is designed as an optically transparent material. According to this exemplary embodiment, the compensation element 110 is formed at least partially or completely from plastic. According to one exemplary embodiment, the compensation element 110 is formed entirely from plastic. According to this exemplary embodiment, the compensation element 110 is formed in one piece and/or from one material. The compensation element 110 can also have a further material such as an anti-reflection coating applied to one or more relevant surfaces.

According to an alternative exemplary embodiment, the compensation element 110 is arranged in direct contact with the image sensor 120 or lens or optical element 115 . It is to be understood as direct that, with the exception of an optional fastening material, no other component is contacted between the compensation element 110 and the image sensor 120 or lens or optical element 115 . It is also conceivable that the compensation element is arranged or applied on or in the optical element such as the lens.

• Die hier vorgestellte Kompensationsvorrichtung 100 ermöglicht vorteilhafterweise eine Defokus-Kompensation des Fokusshifts/Fokusverschiebung in Kameras mit Hilfe eines optischen Kompensationselements 110.

Details of the compensation device 100 are described in more detail below:

• The compensation device 100 presented here advantageously enables defocus compensation of the focus shift/focus shift in cameras with the aid of an optical compensation element 110.

Cameras are increasingly being installed in vehicles 130 in the automotive industry. These cameras are used, for example, for driver assistance or for automated driving. The image data is evaluated by algorithms that require a minimum level of image sharpness. The area in which the image is sharply imaged by a lens or optical element 115 is very small. It is typically in the range of approx. 10-100 µm (depth of focus, DOF) for automotive cameras. In order to produce a sharp image, the image sensor 120 must be positioned in this area. Due to the strong mechanical and thermal loads on automotive cameras, these have so far been designed as fix-focus systems and can no longer be refocused, as is the case e.g. B. is possible with consumer products.

1. 1. Anpassung des Temperaturshifts von Objektiv und Mechanik aufeinander
2. 2. Vorhalt eines möglichst großen Schärfebereichs „Depth of Focus“, DOF. Das heißt, dass der „akzeptabel scharfe Bereich“ vor und hinter der eigentlichen Bildebene möglichst groß sein soll.

However, there are many influences that can defocus a camera. One of the influences is the change in focus position over temperature. Automotive cameras have to be sharp in a temperature range of -40° to +105°C. This is a major challenge due to the expansion of mechanical components and the change in the optical properties of the lens materials. The following two approaches are therefore pursued during the development of the cameras:

1. 1. Adaptation of the temperature shift of lens and mechanics to each other
2. 2. Preservation of the largest possible sharpness range "Depth of Focus", DOF. This means that the "acceptably sharp area" in front of and behind the actual image plane should be as large as possible.

1. Adjusting the temperature shift of lenses and mechanics exactly to each other is very difficult. Your adjusting screws are mainly the change of materials or the mechanical arrangement. Compared to the requirement (it is often about a setting in the range of a few µm), this is quite rough and often unsuccessful.

• - Erhöhte Kosten durch teurere Materialien, engere Toleranzen, Ausschuss in der Produktion der Objektive
• - Größere Blendenzahlen, d. h., weniger Lichtempfindlichkeit der Objektive
• - Aufwendigeres, teureres Aufbau- und Verbindungskonzept in der Produktion des Kamerasystems

2. A large depth of field is often difficult to combine with the high optical requirements and makes compromises necessary, e.g. e.g.:

• - Increased costs due to more expensive materials, tighter tolerances, rejects in the production of the lenses
• - Larger f-numbers, ie the lenses are less sensitive to light
• - More complex, more expensive construction and connection concept in the production of the camera system

An example of such a camera exhibiting high temperature defocusing is in 2 shown with a diagram.

Current and future camera generations for automotive applications require smaller pixel sizes and f-numbers as well as greater image sharpness. All these requirements make the design of a camera lens and associated mechanics very difficult without additional measures.

The compensation device 100 presented here is advantageously designed to improve/at least partially compensate for the defocusing of the camera. One object of the approach presented here is that an optical element is introduced into the beam path 125 between the lens or optical element 115 and the image sensor 120, the compensation element 110, which also expands thermally or whose optical properties also change as a result of expansion/change of the refractive index and thus at least partially or completely compensates for the focus shift of the camera module.

The introduction of the compensation element 110 in the form of an optically active element in the focused beam path 125 causes a defocusing of the beam path 125. This defocusing depends on the refractive index and on the thickness of this element 110. The focus shift is adjustable by changing the thickness.

so wird auch der Fokus um Δz abhängig vom Brechungsindex n verschoben. Für kleine Einfallswinkel gilt näherungsweise: $$\Delta z=\Delta d\frac{n-1}{n}$$

$$\Delta z=d_{HT}\frac{n_{HT}-1}{n_{HT}}-d_{TT}\frac{n_{TT}-1}{n_{TT}},$$

wobei der Index HT eine Hochtemperatur, der Index TT eine Tieftemperatur, die Variable n den Brechungsindex und die Variable d eine Dicke des betrachteten Materials repräsentiert.If the thickness d ₀ of the material of the compensation element 110 with a thermal expansion coefficient CTE now changes by Δd due to a temperature change ΔT $$\Delta \mathrm{i.e}=CTE\cdot {\mathrm{i.e}}_0\cdot \Delta T$$

the focus is also shifted by Δz depending on the refractive index n. For small angles of incidence, the following applies approximately: $$\Delta \mathrm{e.g}=\Delta \mathrm{i.e}\frac{n-1}{n}$$

$$\Delta \mathrm{e.g}={\mathrm{i.e}}_{HT}\frac{n_{HT}-1}{n_{HT}}-{\mathrm{i.e}}_{TT}\frac{n_{TT}-1}{n_{TT}},$$

where the index HT represents a high temperature, the index TT a low temperature, the variable n the refractive index and the variable d a thickness of the material under consideration.

If such a compensation element 110 z. B. brought as a plane-parallel plate between lens or optical element 115 and sensor 120, the focus / depth of field of the lens or optical element 115 is additionally shifted when heated. The desired additional focus shift can be set very precisely by selecting the thickness d ₀ , so that the sensor 120 is within the depth of field range in every temperature range, see FIG 3 .

In this way, the discrepancy or mismatch between mechanical and optical design can be (partially) compensated. Particularly in the case of modular systems in which a camera mechanism is used for different lenses or optical elements 115, the lens shift of the different lenses or optical elements 115 can be adapted, thus preventing time-consuming iterations in lens development, or directly off-the-shelf design are used.

• - Die gleiche optische Wirkung wird statt durch Dickenänderung durch eine Brechzahländerung des optischen Kompensationselements 110 erzeugt.
• - Neben der Kompensation eines Temperatur-induzierten Fokus-Shifts ist eine Kompensation eines Feuchte-induzierten Fokus-Shifts durch Wahl eines geeigneten Materials (Ausdehnung durch Feuchteaufnahme), realisiert.
• - Das optische Element 110 ist als planparallele Platte oder als Linsenelement ausgeführt. Planparallele Platten sind unempfindlich gegen Dezentrierung und Positionsänderungen in z-Richtung. Linsenelemente können die optische Performance des Systems zusätzlich verbessern.
• - Das optische Element 110 ist an beliebiger z-Position zwischen Objektiv bzw. optischem Element 115 und Sensor 120 eingebracht. Denkbar sind z. B. eine Lens-on-Chip im direkten Kontakt mit dem Sensor 120, beispielsweise als Ersatz für ein Sensor-Deckglas und/oder als Add-on auf einen oder als Ersatz für einen IR-Filter des Objektivs bzw. optischem Element 115.
• - Neben passiven Elementen 110, die sich durch Temperatur und/oder Feuchte ausdehnen, ist zusätzlich oder alternativ eine aktive Komponente, die z. B. durch Anlegen einer Spannung die Dicke oder die Brechzahl ändert, realisiert, was als aktiver Autofokus bezeichnet werden kann.

According to an exemplary embodiment, the compensation device 100 has at least one or any combination of the following variants:

• The same optical effect is produced by changing the refractive index of the optical compensation element 110 instead of by changing the thickness.
• - In addition to the compensation of a temperature-induced focus shift, a compensation of a moisture-induced focus shift is realized by selecting a suitable material (expansion through moisture absorption).
• - The optical element 110 is designed as a plane-parallel plate or as a lens element. Plane-parallel plates are insensitive to decentering and changes in position in the z-direction. Lens elements can further improve the optical performance of the system.
• - The optical element 110 is inserted at any desired z-position between the lens or optical element 115 and the sensor 120. Conceivable are z. B. a lens-on-chip in direct contact with the sensor 120, for example as a replacement for a sensor cover glass and/or as an add-on to or as a replacement for an IR filter of the lens or optical element 115.
• - In addition to passive elements 110, which expand due to temperature and / or humidity, is additionally or alternatively an active component z. B. changing the thickness or the refractive index by applying a voltage, realized what can be referred to as active autofocus.

Areas of application for the compensation device 100 presented here are: automotive camera systems, camera systems in the consumer sector such as smartphones and/or consumer cameras, cameras for professional applications, e.g. B. Science such as space travel, aviation (also air taxis), surveillance cameras.

In summary, thanks to compensation device 100, an optically effective element 110 is introduced into beam path 125 for stabilizing a focus point 127 in a camera module, which, according to one exemplary embodiment, has a similar or identical effect, for example a refraction or deflection effect, to thermal expansion of a mount or A holding element 128 of the image sensor 120. A shift in the focal point 127 of the camera module can thus be compensated for by the similar or opposite effect of the optically active element 110 on the beam formation.

2 shows a schematic representation of a thermally induced focus shift in a camera. It can be a camera without the in 1 Act compensation element 110 described. The focus shift, also called "focus shift" or "defocusing", is shown in µm over the temperature in °C.

Shown is an example of a camera exhibiting high and low temperature defocusing.

3 FIG. 1 shows a schematic comparison of a compensation device 100 according to an exemplary embodiment compared to an optical system 300 without an optical compensation element. This can be one of the compensation devices 100 described with reference to the previous figures. Image sections a) and b) each show an optical system 300 without an optical compensation element and image sections c) and d) each show a compensation device 100, ie the optical system 300 with an optical compensation element 110.

Image section a) shows that the image sensor 120 of the optical system 300 is at 20° C. in the depth of field DOF, ie in focus. A sharp image emerges.

Image section b) shows that the image sensor 120 of the optical system 300 is at 105° C. outside the depth of field DOF, ie not in focus. As the temperature increases, the image sensor position is shifted relative to the DOF - both can and usually do move over temperature. The image sensor is outside the DOF depth of field, resulting in a blurred image.

Image section c) shows that the image sensor 120 of the compensation device 100 is at 20° C. in the depth of field DOF, ie in focus. A sharp image emerges.

Image section d) shows that the image sensor 120 of the compensation device 100 is at 105° C. in the depth of field DOF, ie in focus, since this was shifted by the compensation element 110 . When the temperature increases, the image sensor position is shifted. The depth of field DOF is also shifted by the compensation element 110 . The image sensor is still within the DOF depth of field and produces a sharp image.

A suitable material for the compensation element 110 is, for example, transparent plastics of optical quality with a high coefficient of thermal expansion. It exhibits a comparatively high thermal expansion coefficients of at least 50 ppm/K. When introducing the compensation element 110 in the form of a plane-parallel plate with a thickness of 1 mm in the beam path of the optical system, a 4.05 μm large shift and thus a refocusing can be generated when heating from 20° to 105° C., in which approx. 1/3 of the 20µm large focus shift is compensated. This significantly improves the sharpness.

4 shows a schematic representation of a focus shift by an optical compensation element, which changes the refractive index and thickness depending on the temperature according to an embodiment. It can be based on 1 or 3 Act compensation element described.

5 shows a flowchart of a method 500 according to an embodiment for compensating for a focus shift of an optical system. This may be a method 500 performed using any of the methods illustrated in FIG 1 , 3 or 4 described compensation devices is executable.

The method 500 comprises a step 505 of providing and a step 510 of changing. In step 505 of providing, an optical system with a lens or optical element and an image sensor, which are arranged in a common beam path that is focused on a focus point, and an optical compensation element arranged in the beam path are provided. In step 510 of changing, an optical effect of the compensation element is changed in response to at least one environmental parameter in order to shift the focus point in order to compensate for the focus shift of the optical system. According to one exemplary embodiment, in step 510 of changing, an electrical voltage is applied in response to the at least one environmental parameter in order to change the optical effect of the compensation element in order to shift the focus point in order to compensate for the focus shift of the optical system.

The method steps presented here can be repeated and carried out in a different order than the one described.

6 shows a flowchart of a method 600 according to an embodiment for producing a compensation device for compensating for a focus shift of an optical system. This can be one of the compensation devices described with reference to the previous figures.

The method 600 comprises a step 605 of providing and a step 610 of arranging. In step 605 of providing, the optical system is provided with a lens or optical element and an image sensor, which are arranged in a common beam path that is focused on a focal point. In the arranging step, an optical compensation element is arranged in the beam path, the optical compensation element being designed to change an optical effect in response to at least one environmental parameter, in order to shift the focus point in order to compensate for the focus shift of the optical system.

7 FIG. 7 shows a block diagram of a device 700 according to an embodiment for compensating for a focus shift of an optical system.

The device 700 comprises a unit 705 for providing and a unit 710 for changing. An optical system with a lens or optical element and an image sensor, which are arranged in a common beam path that is focused on a focus point, and an optical compensation element arranged in the beam path are provided in the unit 705 for providing. In the unit 710 for changing, an optical effect of the compensation element is changed in response to at least one environmental parameter in order to shift the focus point in order to compensate for the focus shift of the optical system. According to an exemplary embodiment, an electrical voltage is applied in unit 710 for changing in response to the at least one environmental parameter in order to change the optical effect of the compensation element in order to shift the focus point in order to compensate for the focus shift of the optical system.

8th shows a block diagram of a device 800 according to an embodiment for producing a compensation device for compensating for a focus shift of an optical system. This can be one of the compensation devices described with reference to the previous figures.

The device 800 comprises a unit 805 for providing and a unit 810 for arranging. In the unit 805 for providing, the optical system is provided with a lens or optical element and an image sensor, which are arranged in a common beam path that is focused on a focal point. In the arranging unit 810, an optical com compensation element arranged in the beam path, wherein the optical compensation element is designed to change an optical effect in response to at least one environmental parameter in order to shift the focus point in order to compensate for the focus shift of the optical system.

The method steps presented here can be repeated and carried out in a different order than the one described.

If an embodiment includes an "and/or" link between a first feature and a second feature, this should be read in such a way that the embodiment according to one embodiment includes both the first feature and the second feature and according to a further embodiment either only that having the first feature or only the second feature.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102008027721 A1 [0002]

Claims (15)

Compensation device (100) for compensating for a focus shift of an optical system (300), the compensation device (100) having the following features: the optical system (300) with an optical element (115), in particular a lens and an image sensor (120), which are arranged in a common beam path (125) which is focused on a focal point (127); and an optical compensation element (110) arranged in the beam path (125), which is designed to change an optical effect in response to at least one environmental parameter in order to shift the focal point (127) in order to compensate for the shift in focus. Compensation device (100) according to claim 1 , in which the compensation element (110) is thermally, moisture-induced and/or stress-induced deformable and/or is designed to change a refractive index thermally, moisture-induced and/or stress-induced. Compensation device (100) according to one of the preceding claims, in which the optical compensation element (110) comprises a material which is designed to expand in a defined temperature range, humidity range and/or electrical voltage range with a predetermined coefficient of expansion. Compensation device (100) according to one of the preceding claims, in which a displacement parameter (Δz ₁ ) of the optical compensation element (110) representing a displacement of the focal point (127) corresponds within a tolerance range to a further displacement parameter (Δz ₂ ) of one of the optical element (115), a holding element (128) of the optical element (115) and/or the image sensor (120) corresponds to the system, the displacement parameter (Δz ₂ ) depending on a refractive index and a coefficient of expansion. Compensation device (100) according to one of the preceding claims, in which the optical compensation element (110) has at least one plane-parallel plate and/or is designed as a plane-parallel plate. Compensation device (100) according to one of the preceding claims, in which the optical compensation element (110) has at least one lens and/or is designed as a lens or as an element with a spherical, aspherical or free form. Compensation device (100) according to one of the preceding claims, in which the compensation element (110) has an optically transparent material and/or is designed as an optically transparent material. Compensation device (100) according to one of the preceding claims, in which the compensation element (110) is formed at least partially from plastic and/or the compensation element (110) has a thermal expansion coefficient of at least 50 ppm/K. Compensation device (100) according to one of the preceding claims, in which the compensation element (110) is coated with an anti-reflective coating. Compensation device (100) according to one of the preceding claims, in which the compensation element (110) is arranged in direct contact with the image sensor (120). Method (500) for compensating for a focus shift of an optical system (300), the method (500) comprising the following steps: Providing (505) an optical system (300) with an optical element (115) and an image sensor (120) which are arranged in a common beam path (125) which is focused on a focal point (127), and one in which Beam path (125) arranged optical compensation element (110); and Changing (510) an optical effect of the compensation element (110) in response to at least one environmental parameter in order to shift the focal point (127) in order to compensate for the shift in focus. Method (600) for producing a compensation device (100) for compensating for a focus shift of an optical system (300), the method having the following steps: providing (605) the optical system (300) with an optical element (115) and an image sensor (120) which are arranged in a common beam path (125) which is focused on a focal point (127); and arranging (610) an optical compensation element (110) in the beam path (125), wherein the optical compensation element (110) is designed to change an optical effect in response to at least one environmental parameter in order to shift the focus point (127), to compensate for the focus shift. Device set up to carry out the steps (505, 510; 605, 610) of one of the methods (500; 600) according to claim 11 or 12 to be executed and/or controlled in appropriate units. Computer program that is set up to carry out the steps (505, 510; 605, 610) of one of the methods (500; 600) according to claim 11 or 12 execute and/or control. Machine-readable storage medium on which the computer program Claim 14 is saved.

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